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A week during which men can engage in manly activities and espouse misogynist beliefs without fear of backtalking females. Unlike the female phenomenon, it is non-cyclical and can occur at any time; but only once per calender month.
"No, honey, I can't mow the lawn today. I'm on my anti-period so I'm going to drink beer and watch football with the guys."
by infested June 13, 2008